Blood typing is used to determine an individual's blood group, to establish whether a person is blood group A, B, AB, or O and whether he or she is Rh positive or Rh negative.
Blood typing may be used to:
- Ensure compatibility between the blood type of a person who requires a transfusion of blood or blood components and the ABO and Rh type of the unit of blood that will be transfused. Blood typing is often done in conjunction with other tests such as an RBC antibody screen and a crossmatch to determine what type of blood or blood components the person can safely receive. A potentially fatal transfusion reaction can occur if a unit of blood containing an ABO antigen to which the blood recipient has an antibody is transfused to the recipient. For example, people with blood group O have both anti-A and anti-B antibodies in their blood. If a unit of blood that is group A, B, or AB is transfused to this person, the antibodies in the recipient's blood will react with the red blood cells, destroying them and causing potentially serious complications.
Similarly, if an Rh-negative individual is transfused with Rh-positive blood, it is likely that the person will produce antibodies against Rh-positive blood. Although this situation does not cause problems for the recipient during the current transfusion, a future transfusion with Rh-positive blood could result in a serious transfusion reaction.
- Determine compatibility between a pregnant woman and her developing baby (fetus). Rh typing is especially important during pregnancy because a mother and her fetus could be incompatible. If the mother is Rh-negative but the father is Rh-positive, the fetus may be positive for the Rh antigen. As a result, the mother's body could develop antibodies against the Rh antigen. The antibodies may cross the placenta and cause destruction of the baby's red blood cells, resulting in a condition known as hemolytic disease of the fetus and newborn (HDFN). To prevent the development of Rh antibodies, an Rh-negative mother is treated with an injection of Rh immune globulin during her pregnancy and again after delivery if the baby is Rh-positive. The Rh immune globulin binds to and "masks" the fetus's Rh antigen during pregnancy and delivery and prevents the mother from developing antibodies against the Rh antigen.
- Determine the blood group of potential blood donors at a collection facility. Units of blood collected from donors are blood typed and then appropriately labeled so they can be used for people that require a specific ABO group and Rh type.
- Determine the blood group of potential donors and recipients of organs, tissues, or bone marrow, as part of a workup for a transplant procedure. Along with HLA testing, ABO blood typing is used to identify and match organ and tissue transplant donors with recipients who have the same or an acceptable number of matching HLA genes and antigens.